Frequency signals include various signals in different bands, such as high-frequency signals, intermediate-frequency signals, and low-frequency signals. Frequency signals are widely applied in the field of display technology, such as, a high-frequency signal is typically used as a clock signal, a calibration signal or a carrier signal, and a low-frequency signal is typically used as a test signal.
The frequency signal is so widely used, and a variety of different frequency signals are generated by different signal generating devices or systems, whereby various signal generating devices or systems, each of which has a certain performance and specification, occur. Currently, a frequency signal can be generated by adopting an analog device or in digital synthesis device.
An analog device is typically a circuit composed of discrete components such as a transistor, a resistor, a capacitor, etc., the frequency signal generated by the analog devices is not high in stability, difficult to debug, and can not accurately control the frequency step. The digital synthesis device is typically a circuit composed of a frequency control word register, a phase accumulator, a sine lookup table, a digital/analog converter, and a programmable logic device such as a direct digital frequency synthesizer (DDS) chip or a field programmable gate array (FPGA), the digital synthesis device can generate frequency signals with arbitrary waveforms and more precise step frequency, and the stability of the generated frequency signal is relatively high, but the digital synthesis device is expensive.
Therefore, how to design a frequency signal generating system which is low in cost and can generate precisely controllable and stable frequency signals becomes a technical problem to be solved currently.